Piston rings



R. M. SHEPARD May 4, 1965 PISTON RINGS 2 Sheets-Sheet 1 Filed June 30, 1958 INVENTOR. Ra/ph M Shepard ATTORNEYS May 4, 1965 R. SHEPARD PISTON RINGS 2 hee s-s 2 Filed June so, 1958 INV R ph BY United States Patent 3,181,875 PISTGN nnvos Raiph M. Shepard, Mushegon Heights, Mich, assignor to l dnslregon Piston Ring Company, Muskegon, Mich, a corporation of Michigan Filed June 3d, 1958, Ser. No. 745,448 8 Ciainis. (Cl. 277--14ti) This invention relates to piston rings of the three component type having a pair of parted rails and a parted, resilient spacer-expander for supporting the rails. More particularly, this invention is directed to the construction of the spacer-expander.

In the design and manufacture of automotive engines, a wide variety of design requirements are encountered in the piston ring field. These involve a variety of degrees of flexibility of the ring and a wide variety in the depth of the ring groove. These various design requirements have frequently confronted ring design personnel with conflicting physical and performance requirements. Heretofore, where the ring groove was deepened, it was necessary to increase correspondingly the radial depth of the ring to prevent excessive necklacing. As a result, the ring became less flexible and lacked essential operational characteristics.

This invention resolves this problem by a novel structure which divorces the depth of the rails from the depth of the spacer-expander. Thus, the radial depth of the spacer-expander may be varied to match the depth of the ring groove involved without varying the radial depth of the rails. A piston ring may be constructed with this invention having a substantial radial depth to meet the requirements of a deep ring groove yet utilize rails of narrow radial depth characterized by a high degree of fiexibility. This is particularly advantageous in providing a piston ring having highly efiicient operating characteristics and at the same time adapted to easy installation. Further, this variation in the depth of the ring may be made without changing the fundamental design of the spacerexpander. In fact, it may be acomplished by changing only one simple die of the several dies required to form the spacer-expander blank. Thus, the cost of adapting the ring is reduced to a minimum.

The ring has an added advantage of being characterized by a high degree of openness. That is, of the total area of the spacer-expander, a larger proportion of it is open as compared with more conventional designs. This substantially improves its operational characteristics by reducing its tendency to clog with carbon deposits. The more open the ring, the longer its efficient operating life.

These and other objects and purposes of this invention will be immediately understood by those acquainted with the design, manufacture and use of piston rings upon reading the following specification and the accompanying drawings.

In the drawings:

FIG. 1 is a fragmentary view of a strip of stock illustrating from left to right in progressive order the cuts made in the stock to form the basic blank from which the spacer-expander is bent and coiled.

FIG. 2 is a plan view of a piston ring incorporating this invention with a portion of the rails broken away.

FIG. 3 is an enlarged fragmentary oblique view of the spacer-expander.

FIG. 4 is a fragmentary sectional elevation View of the spacer-expander installed in the ring groove of a piston.

FIG. 5 is a fragmentary view of a blank for a modified spacer-expander structure.

FIG. 6 is an enlarged fragmentary oblique View of the modified spacer-expander.

3,l8l,875 i atented May 4, 1965 FIG. 7 is a fragmentary sectional elevation view of the modified spacer-expander installed in a ring groove.

In executing the objects and purposes of this invention, a piston ring is provided having a pair of parted rails and a parted, resilient expander-spacer. The expanderspacer is formed from a ribbon of suitable material and consists of a plurality of annuli arranged in tandem and joined along the center axis of the ribbon by small connecting webs. The annuli are rectangular in configuration and each has a pair of tongues which, when the formed blank is bent into U-shape, extend radially from one edge of the ring. The free ends of these tongues are turned outwardly from the ring to engage the radially inner edge of the rails. The outer side portions of the annuli, after forming into U-shape, form the rail seats with the connecting webs and the adjacent portions of the sides of the annuli forming the web or bight of the U-shaped cross section of the expander-spacer.

Referring specifically to the drawings, the numeral 1 indicates a ribbon of material such as a spring steel or other material having suitable resilient characteristics (FIG. 1). To form the spacer-expander of this invention, the ribbon 1 is provided with pairs of slits 2 equally spaced longitudinally of the ribbon. The pairs of slits 2 are aligned laterally of the ribbon and open through opposite edges of the ribbon with a portion of the ribbon left intact between their inner ends to form connecting webs 3. The connecting webs 3 are centered about the longitudinal axis of the ribbon. The forming of the slits 2 leaves the ribbon as a plurality of connected rectangular blocks 4.

A pair of rectangular apertures S are next formed in each of the blocks 4 extending laterally of the ribbon. The apertures 5 are spaced apart at the center of the block 4, leaving a connecting bar 6. The center portions of the bars are then removed to provide the longitudinally extending aperture '7 connecting the two apertures 5 in each block 4. This operation converts each of the blocks 4 in a rectangular annulus 8 having a generally H-shaped central opening. Each annulus 53 has a pair of oppositely and inwardly extending tongues 9 at its center portion.

It will be seen that the annuli 8 formed in these steps have parallel walls both laterally and longitudinally of the blank and are joined to each other only along the center line by the webs 3. The ends of the tongues 9 are each bent sharply to the plane of the blank to form tangs or tabs 10. The blank is then bent into a U-shaped cross sectional configuration along two lines 11 and 11a. The bending along the lines 11 and 11a is done in such a fashion that when the spacer has been formed to its final shape, the tabs lit extend outwardly from the spacer-expander.

After forming into the U-shape, the outerside portions of the annuli 8 become the rail seats 12 and 12a (FIG. 3). These are parallel and spaced apart a sufiicient distance to hold the rails properly within the ring groove. The outer edges of the annuli become the radially outer edges of the spacer-expander with the center portion of the annuli together with the connecting webs 3 serving as the bight portion 15 or inner radial edge of the spacer-expander. It will be noted that the spacer-expander has continuity of structure only along the bight portion 15. This creates a highly flexible structure yet one which is capable of producing substantial radial tension.

In the completed ring both rails and the spacer-expander are parted at (FIG. 2). This parting in the rails is closed or substantially closed when the ring is installed. This parting is closed in the installed spacer-expander and its ends butt. This is necessary to create radial tension in the spacer so it will urge the rails 2i against the cylinder walls.

It will be noted that piston rings utilizing spacer-expanders of this invention have a high degree of openness. Substantially the entire radial inner wall or bight portion 15 of the structure is open, together with a major portion of the rail seats 12. This greatly reduces the accumulation of carbon deposit on the ring with a corresponding increase in the effective life of the piston ring. The openness of the rail seats reduces friction between the rails and the seats. The rails, thus, have greater freedom of movement for following the contour of the cylinder walls. This design permits this high degree of openness to be accomplished without sacrificing of essential strength and body structure adequate to develop the required radial tension and to properly support and space the rails.

The position of the tangs or pads 10 with respect to the inner and outer radial peripheries of the spacer will depend upon the length of the tongues 9. Thus, the narrower the slot 7 cut from the center of the bar 6, the longer will be each of the tongues 9. The longer the tongue, the greater the space between the pad 10 and the outer radial margin of the spacer-expander and thus the deeper must be each of the rails 26. If a rail 20 of substantial radial depth is to be employed, a long tongue 9 will be used. Correspondingly, if a radially shallow rail 26 is to be employed, the tongue is correspondingly I shortened. It will be seen that the location of the tang or pad 10 is not dependent upon the radial depth of the spacer or of the rail seats 12 and 12a. Thus, this invention makes it possible to utilize rails 20 of shallow radial depth with a spacer having proportionally greater radial depth to prevent necklacing. Simply by relocating the pads 10 with relation to the radially outer periphery of the spacer it may be adapted to rails of various radial depths. Further, this change requires no expensive tooling change. The die employed for removing the center of the bar 6 is simply exchanged for one having a greater or lesser width, depending upon the length of tongue desired. This involves the substitution of one of the most simple of all forms of tools and the minor nature of the change is such that it may be made with a minimum of production delay. This separation of the radial depth relationships of the spacer from that of the rails has not been accomplished before nor has it been possible to make such a major variation in the characteristics of the piston ring with so minor a tool change.

The pads 10 may be bent to a position normal to the plane of the rail seats 12 and 12a. However, they are preferably inclined at a slight angle, as illustrated in FIG. 4. With the pads 16 so inclined, their engagement upon the inner radial edge of the rails will, by reason of the tension of the ring, cause the rails to be forced sideways against the walls 21 and 22 of the ring groove 23 as well as outwardly against the cylinder wall 26. This creates what is known as wedging action, improving the side sealing action of the rails in the ring groove. While this inclination of the pads 10 is shown and described, it is not a part of this invention.

FIGS. 5, 6 and 7 illustrate a modified form of this invention. The blank 36 for this spacer-expander is illustrated in FIG. 5 and is generally similar to the blank illustrated in FIG. 1. It consists of a plurality of generally rectangular annuli 8a joined along the central axis of the blank by connecting webs 3a. Each annulus 8a has a generally H-shaped central opening 31 oriented transversely of the annulus. Each annulus has a pair of transversely aligned and oppositely and inwardly extending tongues 9a.

Each marginal edge of the annulus is provided with a notch 32 elongated axially of the blank 30. An outwardly projecting ear 33 is left at each end of each of the notches 32, giving the blank a generally scalloped edge. The annuli are separated and defined from each other by slits 2a. These slits are arranged in pairs, aligned transversely of the blank and extend from each marginal edge to terminate at the connecting webs 3a.

The blank 30 is formed along fold lines 11 and 11a parallel to its marginal edges with the connecting webs 3a centered along the web or bight 34 of the resulting U- shaped structure. The formed blank is then coiled with the bight 34 on the radial outer margin of the spacer-expander. The outer side portions of the annuli thus become rail seats 35 and 35a of the spacer-expander. The ears 33 become the radial inner edge of the spacer-expander. As such, they serve to give the spacer-expander sufficient radial depth to prevent necklacing in the ring grooves at the time of installation, without reducing the resiliency and flexibility of the spacer-expander. This is important because excessive necklacing seriously interferes with proper and efficient ring installation. In some cases it results in damage to or twisting of the ring. Such rings are ineffective in providing a seal between the combustion chamber and the crankcase.

The ears have another important advantage. The depth of the ring can be varied as required, simply by retaining the same aperture pattern while substituting a wider ribbon of stock. This will result in deeper notches 32 and longer cars 33 but the radial width of the material between the ends of the central openings 31 and the bottoms of the notches 32, which determine the flexibility of the spacer-expander, will remain the same.

The tongues 9a are bent outwardly from the spacerexpander to form tabs 10a. Since the tongues 91 extend radially outwardly, they are shorter than those illustrated in FIG. 3 and do not lie under the rails. The out turned tabs Etta on the ends of the tongues butt against the inner radial edge of the rails rather than hook about them. However, the advantage of quick adaptability of the tongues for rails of various radial depths is retained. They may be adjusted in this respect simply by increasing or decreasing their length and varying the distance from the center of the blank 39 at which the tabs 10a are formed.

It will be seen that this invention provides a particularly inexpensive, flexible and adaptable spacer-expander for use in three piece piston rings. It is particularly economical to adapt from one ring groove depth to another. Further, this may be done without changing the radial depth of the rails and thus the flexibility of the ring as a whole. This spacenexpander is particularly adapted to mass production since it may be completely formed as a flat ribbon and then passed continuously through suitable equipment to bend it to the U-shaped cross sectional configuration and coiled to ring shape. This reduces the complexity of its manufacture and permits its manufacturing costs to be held to a minimum. It will be recognized that various modifications of this invention may be made, each within the principles of the invention. Such modifications are to be considered as included in the hereinafter appended claims, unless these claims, by their language, expressly state otherwise.

I claim:

1. A spacer for a piston ring comprising: a plurality of annuli spaced from each other; a web centered between a pair of opposed sides of each of said annuli and integrally joining each of said annuli to each adacent annulus; said webs being on the inner circumferential periphery of said spacer; each of said annuli being bent along two lines extending longitudinally of said spacer, one on each side of said webs whereby said spacer has a generally U-shaped cross sectional configuration and said opposed sides constitute the outer circumferential periphery of said spacer; a tongue extending radially inwardly from each of said opposed sides; the inner ends of said tongues being bent axially outwardly from said spacer.

2. A spacer for a piston ring comprising: a plurality of rectangular annuli spaced from each other; a Web centered between a pair of parallel sides of each of said annuli and integrally joining each of said annuli to each adjacent annulus; said webs being on the inner circumferential periphery of said spacer; each of said annuli being bent upon along two lines extending longitudinally of said spacer, one on each side of said webs whereby said spacer has a generally U-shaped cross sectional configuration and said parallel sides constitute the outer circumferential periphery of said spacer; rail stop means at the inner radial periphery of said ring.

3. A spacer for a piston ring comprising: a plurality of annuli bent into a generally U-shape with the legs of said U forming spaced rail seats; said annuli being joined to each other along the base of said U, said base forming the radially inner periphery of said spacer and opposed sides of said annuli forming the radially outer periphery of said spacer; a tongue extending radially inwardly from each of said opposed sides of each annuli; the inner ends of said tongues being bent axially outwardly from said spacer.

4. A spacer for a piston ring comprising: a plurality of rectangular annuli bent into a generally U-shape with the legs of said U forming spaced rail seats; said annuli being joined to each other along the base of said U, said base forming the radially inner periphery of said spacer and opposed sides of said annuli forming the radially outer periphery of said spacer; rail stop means at the inner radial periphery of said ring.

5. A spacer for a piston ring comprising: a plurality of annuli spaced from each other; a web centered between a pair of opposed sides of each of said annuli and integrally joining each of said annuli to each adjacent annulus; each of said annuli being bent along two lines extending longitudinally of said spacer, one on each side of said webs whereby said spacer has a generally -U- shaped cross sectional configuration and said opposed sides constitute the inner periphery of said spacer; a tongue having a free end extending radially outwardly from each of said opposed sides; the free ends of said tongues being bent axially outwardly from said spacer whereby they are adapted to serve as rail stops.

6. A spacer for a piston ring comprising: a plurality of rectangular annuli bent into a generally U-shape with the legs of said U forming spaced rail seats; said annuli being joined to each other along the base of said U, said base forming the radially outer periphery of said spacer and opposed sides of said annuli forming the radially inner periphery of said spacer; rail stop means integral with said opposed sides intermediate the inner and outer peripheries of said spacer.

7. A spacer for a piston ring comprising: a plurality of annuli spaced from each other; a web centered between a pair of opposed sides of each of said annuli and integrally joining each of said annuli to each adjacent annulus; each of said annuli being bent along two lines extending longitudinally of said spacer, one on each side of said webs whereby said spacer has a generally U- shaped cross sectional configuration and said opposed sides constitute the inner periphery of said spacer; a tongue having a free end extending radially outwardly from each of said opposed sides; the free ends of said tongues being bent axially outwardly from said spacer whereby they are adapted to serve as rail stops; a radially inwardly projecting ear on each of said sides adapted to engage the bottom of a ring groove to limit necklacing when the spacer is installed.

8. A spacer for a piston ring comprising: a plurality of annuli spaced from each other; a web centered between a pair of opposed sides of each of said annuli and integrally joining each of said annuli to each adjacent annulus; each of said annuli being bent along two lines extending longitudinally of said spacer, one on each side of said webs whereby said spacer has a generally U- shaped cross sectional configuration and said opposed sides constitute the inner periphery of said spacer; a tongue having a free end extending radially outwardly from each of said opposed sides; the free ends of said tongues being bent axially outwa-rdly from said spacer whereby they are adapted to serve as rail stops; a pair of radially inwardly projecting ears on each of said sides, one at each end of each of said sides; said ears being adapted to engage the bottom of a ring groove to limit necklacing when the spacer is installed.

References Cited by the Examiner UNITED STATES PATENTS 2,482,990 9/49 Olson 29-190 2,568,655 9/51 Olson 309-44 2,760,835 8/56 Shirk 309-44 2,999,728 9/ 61 Estey 277-139 LEWIS I. LENNY, Primary Examiner.

KARL J. ALBRECHT, RALPH H. BRAUNER, SAM- UEL ROTHBERG, EDWARD V. BENHAM,

Examiners. 

6. A SPACER FOR A PISTON RING COMPRISING: A PLURALITY OF RECTANGULAR ANNULI BENT INTO A GENERALLY U-SHAPE WITH THE LEGS OF SAID U FORMING SPACED RAIL SEATS; SAID ANNULI BEING JOINED TO EACH OTHER ALONG THE BASE OF SAID U, SAID BASE FORMING THE RADIALLY OUTER PERIPHERY OF SAID SPACER AND OPPOSED SIDES FO SAID ANNULI FORMING THE RADIALLY INNER PERIPHERY OF SAID SPACER; RAIL STOP MEANS INTEGRAL WITH 